contrast-agent-p792 and Disease-Models--Animal

The effect of two novel therapeutic agents on tumour haemodynamics was investigated using a fast dynamic contrast-enhanced (DCE)-MRI protocol (0.5 s/image) sensitive to signal changes in both the vascular input function and tumour during the administration of the macromolecular rapid clearance blood pool agent (MM-RCBPA), gadomelitol (P792, Vistarem). This enabled simultaneous measurement of the tumour blood flow per unit volume of tissue (F/V(T), mL/s/mL), the fractional plasma volume (V(p), %), and the permeability surface area product per unit volume of tissue (PSrho, s(-1)) in subcutaneous SW620 human colorectal tumour xenografts grown in nude rats before and after (at 0 and 22 h; imaging at 24 h) acute treatment with AZD2171 (3 mg/kg) and vandetanib (ZD6474, Zactima; 50 mg/kg), which have inhibitory activity against vascular endothelial growth factor receptor-2 (VEGFR-2) tyrosine kinase. MRI was performed at 4.7 T using a single-slice, modified, T(1)-weighted, spoiled gradient-echo technique. Both compounds reduced gadomelitol uptake into the tumour. AZD2171 and vandetanib, respectively, (a) greatly reduced PSrho to 19.7 +/- 9.5% and 28.9 +/- 14.1% of baseline (P = 0.007 and P = 0.02), (b) markedly reduced V(p) to 31.2 +/- 19.1% and 54.8 +/- 21.2% of baseline (P = 0.015 and P = 0.09), and (c) had no significant effect on F/V(T). There was no significant difference between groups treated with AZD2171 and vandetanib when each variable was compared. The reductions in PSrho and V(p) are consistent with inhibition of VEGF signalling. AZD2171 (3 mg/kg) and vandetanib (50 mg/kg) were also found to produce a comparable chronic inhibition of SW620 tumour growth (89% for both). This study shows that DCE-MRI using an MM-RCPBA can be used to distinguish tumour vascular flow, volume, and permeability surface area product in a tumour model, and enables the acute effects of VEGF signalling inhibition to be examined in detail.

Topics: Animals; Calibration; Cell Proliferation; Colonic Neoplasms; Contrast Media; Disease Models, Animal; Heart Ventricles; Hemodynamics; Heterocyclic Compounds; Humans; Magnetic Resonance Imaging; Male; Neoplasm Transplantation; Organometallic Compounds; Piperidines; Quinazolines; Rats; Rats, Nude

To summarize the physicochemical characterization, pharmacokinetic behavior, and biological evaluation of P792, a new monogadolinated MRI blood-pool agent.. The molecular modeling of P792 was described. The r1 relaxivity properties of P792 were measured in water and 4% human serum albumin at different magnetic fields (20, 40, 60 MHz). The stability of the gadolinium complex was assessed. The pharmacokinetic and biodistribution profiles were studied in rabbits. Renal tolerance in dehydrated rats undergoing selective intrarenal injection was evaluated. Hemodynamic safety in rats and in vitro histamine and leukotriene B4 release were also tested.. The mean diameter of P792 is 50.5 A and the r1 relaxivity of this monogadolinium contrast agent is 29 L x mmol(-1) x s(-1) at 60 MHz. The stability of the gadolinium complex in transmetallation is excellent. The pharmacokinetic and biodistribution profiles are consistent with that of a rapid-clearance blood-pool agent: P792 is mainly excreted by glomerular filtration, and its diffusion across normal endothelium is limited. Renal and hemodynamic safety is comparable to that of the nonspecific agent gadolinium-tetraazacyclododecane tetraacetic acid. No histamine or leukotriene B4 release was found in RBL-2H3 isolated mastocytes.. The relaxivity of P792 at clinical field is very high for a monogadolinium complex without protein binding. The pharmacokinetic and biodistribution profiles are consistent with those of a rapid-clearance blood-pool agent. Its initial safety profile is satisfactory. Experimental and clinical studies are underway to confirm the potential of P792 in MRI.

Topics: Acute Kidney Injury; Animals; Contrast Media; Disease Models, Animal; Hemodynamics; Heterocyclic Compounds; Histamine; Leukotriene B4; Magnetic Resonance Imaging; Magnetic Resonance Spectroscopy; Molecular Structure; Organometallic Compounds; Rabbits; Rats; Tissue Distribution